The proposed research represents an extension of studies conducted in our laboratory. These included determining pulmonary intravascular and extravascular fluid volumes in hemorrhagic shock and following fluid replacement; measuring the effects of methysergide on pulmonary capillary perfusion in experimental pulmonary embolization; evaluating the canine platelet response to regional and systemic shock; and assessing platelet trapping in the lungs of dogs subjected to hemorrhagic shock and/or pulmonary embolization. In dogs, Cr51 platelets, I125 fibrinogen, and plasminogen activators will be determined in the lungs, and the fibrin split products will be assessed in the systemic venous circulation and pulmonary venous effluent. The effects of pulmonary embolization, trauma, and shock will be studied and therapeutic modalities evaluated. A modified Cannon-Bayliss technique to induce soft tissue trauma will be used to create two groups of animals, one with and one without shock. The above-mentioned studies will be performed to determine if alterations are associated with trauma alone or if shock is also required. Pulmonary embolization will then be imposed upon each of these two experimental groups and the studies repeated to test our previous findings that pulmonary embolization in the animal without hemorrhagic shock resulted in lysis of an homologous embolus and absence of platelet trapping, while the embolus persisted in the shocked animal and platelet trapping occurred. Using the model of pulmonary embolization with homologous blood on shocked animals and the same studies plus pulmonary arterial pressure determinations, methysergide, acetylsalicylic acid, dextran, Ringer's lactate to reduce the hematocrit, heparin, and steroids will be evaluated as pretreatment. The results should aid in establishing an applicable clinical approach to pulmonary embolization.